Following the report, shares of Tesla are up more than 5%. SolarCity, of which Tesla CEO Elon Musk is chairman, is also up 2.5%.

Tesla has announced plans to build a gigafactory, which would allow Tesla to make lithium-ion batteries for its cars, and will choose a site by the end of the year. These lithium-ion batteries would also be used as power storage units sold by SolarCity.

In a feature on Tesla's efforts to build a gigafactory, BI's Rob Wile noted that the gigafactory is Musk's biggest bet of his career. The success of Tesla may hinge on the success of the gigafactory. Musk told The Wall Street Journal's Cassandra Sweet that outside of building a gigafactory, Tesla "can't figure out any other way to scale."

That Tesla is in talks with Nissan or BMW shouldn't come as a complete shock, as Musk last week made the unprecedented decision to make the company's patents available for anybody to use.

In making the company's patents available, Musk argued in a blog post that the company doesn't need them because the company's real competition isn't other electric carmakers but cars that run on gasoline.

In his post Musk said, "We believe that Tesla, other companies making electric cars, and the world would all benefit from a common, rapidly evolving technology platform."

On a conference call accompanying Musk's announcement, which was made in a company blog post, he said he spoke to BMW the previous day about ditching their patent protections.

Foy's report quotes an unnamed execute as saying, "It is obviously clear that everyone would benefit if there was a far more simply way for everyone to charge their cars."